Widebeam antennas are used extensively in military and commercial space, aviation and ground applications. Examples of applications of such an antenna include telemetry command and ranging (TC&R) antennas for spacecraft, airborne ground surveillance radar systems or user terminal antennas for global positioning satellite (GPS) receivers. A wideband antenna may also be used as a feed for certain types of reflectors. For example, in compact range applications, in order to minimize amplitude taper and increase a cross-sectional area of a quiet zone volume, a widebeam feed may be desirable. In addition, a widebeam antenna feed may be used in cooperation with a deep reflector antenna having an F/D ratio of about one or less. Desirably, such antennas exhibit quasi-omnidirectional (sometimes referred to as near-isotropic) coverage patterns. Using conventional techniques, however, antennas capable of exhibiting such coverage patterns have been unduly bulky, complex, expensive, and/or difficult to fabricate, tune or maintain or exhibit excessive return loss, particularly where the antenna is required to handle a broad band RF signal, circularly polarized electromagnetic radiation, and/or to exhibit low cross polarization over almost all directions. Conventional techniques also frequently rely on dielectric components, such components being disadvantageous for, at least, spacecraft applications.
Accordingly, an improved widebeam antenna is desirable.